- `[removed]` Drop support for Python 3.5 (34)
- `[added]` Add support for Python 3.9 and 3.10 (50)
- `[changed]` Make the `Ok` type covariant in regard to its wrapped type `T`.
Likewise for `Err` in regard to `E`. This should result in more intuitive
type checking behaviour. For instance, `Err[TypeError]` will get recognized
as a subtype of `Err[Exception]` by type checkers. See [PEP 438] for a
detailed explanation of covariance and its implications.
- `[added]` Add support for Python 3.10 pattern matching (47)
- `[changed]` `Ok` and `Err` now define `__slots__` to save memory (55, 58)
- `[changed]` The generic type of `UnwrapError.result` now explicitly specifies `Any` (67)
[PEP 438]: https://www.python.org/dev/peps/pep-0483/#covariance-and-contravariance